Automobiles in general include subsystems that produce undesirable noise, such as but not limited to air induction systems associated with an internal combustion engine. To attenuate the noise wave generated in an intake air duct of an engine, Helmholtz type resonators have been used that change the volume of the resonator to adjust for varying frequencies of the noise wave as engine speed changes. Such designs, however, either bulky-type side chambers or heavy-type piston-type members coupled to an actuator, which can be also bulky arrangements involving multiple interconnected parts that are susceptible to mechanical wear. In addition, such designs being bulky may not fit the space available for packaging them in an automobile without significant design changes.
In view of the above, it is apparent that there exists a need for an improved Helmholtz type resonator having broader flexibility and improved reliability to attenuate various noise frequencies produced by one of various sources of noise associated with the operation of an automobile, or in any application in which a Helmholtz resonator might be used, especially in those in which the noise frequency is varying with operating RPM or speeds.